A need to use light-weight components as a means to achieve better fuel economies has existed in the automotive and aircraft industries for several years. In addition, there is a growing need to shield out electromagnetic and radio frequency emissions from car radios, truck skid-control braking systems, ignition equipment, microprocessor-based engine-control systems, and systems found in the communication, aerospace, computer, and medical industries. One method for solving these weight and electromagnetic and radio frequency shielding problems is through the electrodeposition of a metallic coating on plastics, commonly called metal electroplating, metal plating, or simply plating. However, metal plating of plastics, as it is currently practiced, involves a long series of time, material, and labor consuming preplating steps as well as a lengthy set of plating steps.
Typically the part to be plated is removed from a forming mold; cleaned thoroughly to remove dirt, fingerprints, particles, die lubricants, etc.; preconditioned to allow for a uniform etch; etched (involving one or more etching and rinsing steps) to afford better metal to plastic adhesion; neutralized of the residues from etching; treated with a catalyst to make the surface more receptive to the deposition of a thin conductive metallic coating on the plastic; treated with an accelerator to promote the effectiveness of the catalyst; coated with a metallic preplate to give the necessary conductivity for the electroplating steps; and plated with copper for 10-20 minutes. The cycle time for the preplating and plating steps is typically in the range of 45 to 60 minutes. Moreover, the etching step necessary to afford metal-plastic adhesion often requires the use of etchable plastics or the addition of etchable materials to the plastic. See, for example, "Plastics Engineering Handbook," 4th edition, 1976, Joel Frados, editor, po. 742-749.
Although the plating of surfaces and the subsequent adhesion of materials to the electroplate to produce metal-clad materials is known (as in Canada Patent 473,507, R. N. Sabee, et. al., May 8, 1951; U.S. Pat. No. 3,649,474, B. E. Blakeslee, et. al., Mar. 14, 1972; U.S. Pat. No. 3,689,729, G. E. Neward et. al., Sept. 5, 1972; IBM Technical Disclosure Bulletin, 1, 14, 60 (June 1971)), problems of long plating times, additional steps, and poor electroplate to material retention have precluded this methodology from gaining widespread acceptance and replacing the aforementioned state of the art. Long plating times have been especially troublesome and rather than use this technique, it has been found that it is more efficient to mold a large number of plastic articles and then plate all of them in a batch process. Coating of surfaces by methods other than electroplating, with the subsequent adhesion of materials to the coating to form coated articles also is known (U.S. Pat. No. Re. 28,068, J. H. Lemelson, July 9, 1974).
High-speed electroplating has been described (U.S. Pat. Nos. 4,053,370, K. Yamashita, et. al., Oct. 11, 1977; 4,080,268, S. Suzuki, et. al., Mar. 21, 1978; 4,119,516, S. Yamaguchi, Oct. 10, 1978; and Plating and Finishing, 7, 68, 52-55 (July 1981)), but it has not been used in conjunction with the high-speed production of metal-clad molded articles.